The invention relates generally to the field of digital data processing systems, and more specifically to distributed monitoring and control systems which may be used in, for example, process control arrangements for controlling large industrial operations such as manufacturing plants or chemical processing plants, environmental monitoring control arrangements for controlling heating, air conditioning, ventilation, illumination, and other controllable environmental factors in industrial, commercial and home environments. The invention particularly provides a controller (called herein a xe2x80x9cfield controllerxe2x80x9d) which provides a compact, computationally-powerful package which is convenient to install and service in a wide variety of environments.
Distributed control systems are often used in a number of commercial, industrial and home applications, in particular to monitor and control operations at manufacturing, chemical processing and similar industrial operations, to monitor and control environmental and other factors and so forth. In a manufacturing operation, a distributed control system will typically control machines which facilitate the manufacture and assembly of the products being manufactured. In addition, in a chemical processing operation, a distributed control system may control valves to control rates of flow of chemicals into and out of reaction chambers, reaction temperatures and pressures and the like which are required to carry out the chemical process. In addition, to controlling the manufacturing or chemical process, distributed control systems may perform bookkeeping operations to keep track of the inventory of inputs required for the manufacturing or chemical process, as well as the inventory of outputs produced by the operation.
Typical distributed control systems essentially comprise large, centrally-located and expensive computer systems. A number of problems arise out of use of such computer systems, including the facts that they are expensive to maintain and typically have limited expansion capabilities.
The invention provides a relatively compact, computationally powerful, easily-extendable and easily-serviceable field controller for use in a variety of industrial, commercial and home applications.
In brief summary, the invention provides a new field controller for use in a distributed control system including an area controller and at least one field controller. The field controller manages at least one controlled device in an industrial process operation. The field controller comprises a processor module segment through which it can control a selected number of devices, and it may also include one or more expansion module segments to enable it to control a larger number of controlled devices. The processor module segment includes a processor module and at least one local interface module for interfacing to a controlled device, and the expansion module segment includes interface modules for interfacing to other controlled devices. In the processor module segment, the processor module and said local interface module are interconnected by a bus segment, which is also connected to an upstream off-module connector. Each expansion module segment includes at least one interface module, and also includes a downstream off-module connector and an upstream off-module connector, which are interconnected by a bus segment. The downstream off-module connector of each expansion module segment is adapted to mate with the upstream off-module connector of the processor module segment and of other expansion module segment, so as to facilitate the interconnection of the processor module segment and a sequence of expansion module segments by establishing a unitary multi-drop bus comprising the processor module""s bus segment and the bus segments of expansion module in the sequence. The processor module controls each controlled device through the respective local interface module or expansion interface module connected thereto. The processor module segment and each expansion module segment are each mounted in a housing segment which is configured to form a unitary housing when they are interconnected.
A benefit of this arrangement is that the number of controlled devices which can be controlled by the field controller be easily increased or decreased by adding expansion module segments to, or removing them from, the field controller. Since the bus created by the series of bus segments is an extensible multi-drop bus, the controlled devices can be connected to the field controller through any interface module connected into the field controller along the bus. Since the processor module segment and each expansion module segment also includes an integral housing segment, when the processor module segment and expansion module segments are connected together they provide a unitary, compact housing which is convenient in a commercial, industrial or home environment.